Field effect transistor devices

ABSTRACT

A memcapacitor device includes a pair of opposing conductive electrodes. A semiconductive material including mobile dopants within a dielectric and a mobile dopant barrier dielectric material are received between the pair of opposing conductive electrodes. The semiconductive material and the barrier dielectric material are of different composition relative one another which is at least characterized by at least one different atomic element. One of the semiconductive material and the barrier dielectric material is closer to one of the pair of electrodes than is the other of the semiconductive material and the barrier dielectric material. The other of the semiconductive material and the barrier dielectric material is closer to the other of the pair of electrodes than is the one of the semiconductive material and the barrier dielectric material. Other implementations are disclosed, including field effect transistors, memory arrays, and methods.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S. patentapplication Ser. No. 13/858,141, filed Apr. 8, 2013, entitled“Memcapacitor Devices, Field Effect Transistor Devices, Non-VolatileMemory Arrays, and Methods Of Programming”, naming Roy E. Meade andGurtej S. Sandhu as inventors, now U.S. Pat. No. 8,867,261, which isfrom a continuation application of U.S. patent application Ser. No.12/705,928, filed Feb. 15, 2010, now U.S. Pat. No. 8,437,174, entitled“Memcapacitor Devices, Field Effect Transistor Devices, Non-VolatileMemory Arrays, and Methods Of Programming”, naming Roy E. Meade andGurtej S. Sandhu as inventors, the disclosures of which are incorporatedby reference.

TECHNICAL FIELD

Embodiments disclosed herein pertain to memcapacitor devices, to fieldeffect transistor devices, to non-volatile memory arrays and to methodsof programming.

BACKGROUND

Capacitors and field effect transistors are two types of electroniccomponents used in integrated circuitry, for example in logic circuitryand memory circuitry. One property of a capacitor is its capacitancewhich is impacted by a number of variables such as size, construction,and materials of manufacture. One property of a field effect transistoris its threshold voltage. Such is a measure of the minimum gate voltagerequired for current to flow between a pair of source/drain regionsthrough a channel region. Factors that impact threshold voltage alsoinclude size, construction and materials of manufacture.

Capacitors and transistors upon manufacture typically have fixedcapacitance and fixed threshold voltage, respectively, as opposed tovariable, adjustable, or programmable capacitance and threshold voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional view of a memcapacitor device in oneprogrammed state, and in accordance with an embodiment of the invention.

FIG. 2 is a view of the FIG. 1 memcapacitor device in another programmedstate in accordance with an embodiment of the invention.

FIG. 3 is a diagrammatic sectional view of a field effect transistordevice in one programmed state, and in accordance with an embodiment ofthe invention.

FIG. 4 is a view of the FIG. 3 field effect transistor device in anotherprogrammed state in accordance with an embodiment of the invention.

FIG. 5 is a diagrammatic top or schematic view of a non-volatile memoryarray in accordance with an embodiment of the invention.

FIG. 6 is a diagrammatic sectional view of the FIG. 3 field effecttransistor device associated in the FIG. 5 memory array in oneprogrammed state and in accordance with an embodiment of the invention.

FIG. 7 is a view of the FIG. 6 field effect transistor device in anotherprogrammed state in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

An example memcapacitor device 10 in accordance with an embodiment ofthe invention is shown in FIGS. 1 and 2. Such show memcapacitor device10 in two different programmed states. Alternate and/or additionalprogrammed states may be used.

Referring to FIG. 1, memcapacitor device 10 comprises a pair of opposingconductive electrodes 12 and 14. Such may be comprised of any suitableconductive material, for example elemental metals, alloys of elementalmetals, conductive metal compounds, and/or conductively dopedsemiconductive materials. Electrodes 12 and 14 may be of the same ordifferent thicknesses. An example thickness range is from 3 nanometersto 100 nanometers. Further, conductive electrodes 12 and 14 may be ofthe same or different composition relative to one another, andregardless may or may not be homogenous. In one example, such mayconsist essentially of elemental platinum.

At least two materials 16 and 18 are received between opposingconductive electrodes 12 and 14. Material 16 is a staticallyprogrammable semiconductive material which comprises mobile dopants thatare received within a dielectric. It is statically programmable betweenat least two different states that are characterized by differentcapacitance values. At least one of the states includes localization orgathering of the mobile dopants such that a dielectric region is formedwithin material 16. More than two programmable states may be used.

In the context of this document, a “mobile dopant” is a component (otherthan a free electron) of the semiconductive material that is movable todifferent locations within said dielectric during normal deviceoperation of repeatedly programming the device between at least twodifferent static states by application of voltage differential to thepair of electrodes. Examples include atom vacancies in an otherwisestoichiometric material, and atom interstitials. Specific example mobiledopants include oxygen atom vacancies in amorphous or crystalline oxidesor other oxygen-containing material, nitrogen atom vacancies inamorphous or crystalline nitrides or other nitrogen-containing material,fluorine atom vacancies in amorphous or crystalline fluorides or otherfluorine-containing material, and interstitial metal atoms in amorphousor crystalline oxides. Mobile dopants of material 16 are depicteddiagrammatically by dots/stippling in the drawings. Density of thedots/stippling in a given area/volume in the drawings indicates degreeof mobile dopant density, with more dots/stippling indicating highermobile dopant density and less dots/stippling indicating lower mobiledopant density. More than one type of mobile dopant may be used as partof material 16.

For material 16, example dielectrics in which the mobile dopants arereceived include suitable oxides, nitrides, and/or fluorides that arecapable of localized electrical conductivity based upon sufficientlyhigh quantity and concentration of the mobile dopants. The dielectricwithin which the mobile dopants are received may or may not behomogenous independent of consideration of the mobile dopants. Specificexample dielectrics include TiO₂, AlN, and/or MgF₂.

In one embodiment, material 16 that comprises oxygen vacancies as mobiledopants may comprise a combination of TiO₂ and TiO_(2-x) in at least oneprogrammed state depending on location of the oxygen vacancies and thequantity of the oxygen vacancies in the locations where such arereceived. In one embodiment, material 16 that comprises nitrogenvacancies as mobile dopants may comprise a combination of AlN andAlN_(1-x) in at least one programmed state depending on location of thenitrogen vacancies and the quantity of the nitrogen vacancies in thelocations where such are received. In one embodiment, material 16 thatcomprises fluorine vacancies as mobile dopants may comprise acombination of MgF₂ and MgF_(2-x) in at least one programmed statedepending on location of the fluorine vacancies and the quantity of thefluorine vacancies in the locations where such are received. In oneembodiment, the mobile dopants comprise aluminum atom interstitials in anitrogen-containing material.

Material 16 may be of any suitable thickness that may be dependent uponthe composition of the dielectric, upon the composition of the mobiledopants, and/or upon the quantity of the mobile dopants in material 16.Example thicknesses include from 4 nanometers to 50 nanometers, and inone embodiment a thickness no greater than 120 nanometers.

Material 18 is a mobile dopant barrier dielectric material. Such may behomogenous or non-homogenous. Mobile dopant barrier dielectric material18 is characterized or distinguished from the dielectric within material16 by both being impervious to movement of mobile dopants to withinmaterial 18 and being impervious to location-changing-movement of anydopants inherently therein. Semiconductive material 16 and barrierdielectric material 18 may be of different composition relative to oneanother which is at least characterized by at least one different atomicelement. In one embodiment, mobile dopant barrier dielectric material 18comprises a metal oxide and the dielectric within which the mobiledopants are received in material 16 comprises another metal oxide,wherein a metal element of material 18 is different from a metal elementof the dielectric of material 16. Regardless, example mobile dopantbarrier dielectric materials include at least one of ZrO₂, SiO₂, Si₃N₄,GeN, and SrTiO₃. In one embodiment, the barrier dielectric materialconsists essentially of stoichiometric metal oxide, for example, eitheror a combination of ZrO₂ and SrTiO₃.

Material 16 and mobile dopant barrier dielectric material 18 may be ofthe same or different thicknesses relative one another. In oneembodiment, mobile dopant barrier dielectric material 18 is no thickerthan material 16, and in one embodiment as shown is thinner thanmaterial 16. In one embodiment, mobile dopant barrier dielectricmaterial 18 has an equivalent oxide thickness from 1 nanometer to 7nanometers, and in one embodiment has an equivalent oxide thickness nogreater than 10 nanometers. In the context of this document, “equivalentoxide thickness” is a linear dimension of how thick undoped silicondioxide would need to be to produce the same dielectric effect as themobile dopant barrier dielectric material being used. Where the mobiledopant barrier dielectric material being used is undoped silicon dioxideor a material of equal permittivity to that of undoped silicon dioxide,the “equivalent oxide thickness” and the thickness of the mobile dopantbarrier dielectric material being used would be the same.

One of semiconductive material 16 and barrier dielectric material 18 iscloser to one of pair of electrodes 12, 14 than is the other ofsemiconductive material 16 and barrier dielectric material 18.Correspondingly, the other of the semiconductive material 16 and thebarrier dielectric material 18 is closer to the other of pair ofelectrodes 12, 14. In the depicted embodiment, material 16 and mobiledopant barrier dielectric material 18 are in physical touching contactwith one another. Further in the depicted embodiment, no other materialis received between the pair of opposing conductive electrodes 12, 14but for material 16 and mobile dopant barrier dielectric material 18.

FIGS. 1 and 2 depict memcapacitor device 10 in two different staticprogrammed states. FIG. 2 diagrammatically depicts an example highestcapacitance state and FIG. 1 depicts an example lowest capacitancestate. For example and by way of example only, FIG. 1 depicts material16 as comprising regions 20 and 22 which are characterized by respectivedifferent average concentration of mobile dopants. Region 22diagrammatically shows a significantly lower quantity of mobile dopantstherein such that region 22 is effectively a dielectric. Some quantityof mobile dopants greater than zero may be within region 22 as long asregion 22 may function in a dielectric capacity. Regardless, region 20has a suitable higher average concentration of mobile dopants than anyconcentration of such within region 22. Any mobile dopants receivedwithin either of region 20 or region 22 may or may not be homogenouslydistributed within the respective region 20 or 22. Regardless, region 20is electrically conductive, thereby effectively providing a thickerconductive capacitor electrode by a combination of material 12 andregion 20. On the other hand, region 22 is dielectric thereby adding tothe effective dielectric thickness of mobile dopant barrier dielectricmaterial 18.

Referring to FIG. 2, the mobile dopants are shown to be sufficientlyreceived throughout all of material 16 such that the entire thicknessthereof is essentially electrically conductive. Accordingly, one of theconductive capacitor electrodes effectively constitutes the combinationof materials 12 and 16. Further, in such state, only mobile dopantbarrier dielectric material 18 constitutes all of the dielectricthickness between conductive capacitor electrodes 12 and 14. Thereby,the programmed state of FIG. 2 has higher capacitance than that depictedin FIG. 1. Further considered or in other words, the capacitance in theFIG. 1 programmed state is lower than the capacitance in the FIG. 2programmed state regardless of an amount of charge actually held bymemcapacitor device 10 at any given moment in time. Whether memcapacitordevice 10 is not charged, partially charged, or fully charged determinesthe charge state of memcapacitor device 10, but does not affect thecapacitance of memcapacitor device 10. Thus, charge state, as usedherein, refers to the amount of charge actually held by a capacitor at agiven moment in time. Capacitance, as used herein, refers to a number ofcoulombs per volt that a capacitor is capable of holding regardless ofthe charge state of the capacitor.

The mobile dopants may or may not be homogenously distributed throughoutmaterial 16 in the FIG. 2 high capacitance state. Further andregardless, different selectable programmed capacitance states beyond orin addition to a highest and lowest capacitance states may be achieved.Regardless, memcapacitor device 10 is characterized at least in part byretaining its programmed capacitance state after the act which providedthe programmed state is removed.

As a specific example capacitor device 10, conductive capacitorelectrodes 12 and 14 each consist essentially of elemental platinumhaving a thickness of 5 nanometers. Mobile dopant barrier dielectricmaterial 18 is ZrO₂ having a thickness of 3 nanometers. Semiconductivematerial 16 is a combination of TiO₂ and TiO_(2-x) and has as an overallthickness of 4 nanometers. In FIG. 1, region 22 has a thickness of 2nanometers and is TiO₂ that has sufficiently less than 5×10¹⁸ oxygenvacancies/cm³ which renders region 22 non-conductive. Region 20 has athickness of 2 nanometers and an overall average oxygen vacancy densitysufficiently greater than 5×10¹⁸ vacancies/cm³ which renders region 20conductive. In FIG. 2, region 16 may be considered as TiO_(2-x) havingan overall average oxygen vacancy density sufficiently greater than5×10¹⁸ vacancies/cm³ which is sufficient to render all of region 16 tobe conductive. Overall average oxygen vacancy density in region 20 inFIG. 1 is greater than that in region 16 in FIG. 2.

The respective capacitances in connection with the FIGS. 1 and 2 modelmay be characterized as:

$C = {A\;\frac{ɛ_{1}ɛ_{2}}{{ɛ_{1}t_{2}} + {ɛ_{2}t_{1}}}}$

where:

-   -   C is the device capacitance    -   A is the area of electrode 14 exposed to material 18.    -   ∈₁ is the permittivity of material 16 characterized by region        22.    -   ∈₂ is the permittivity of material 18.    -   t₁ is the thickness of region 22.    -   t₂ is the thickness of material 18.

The different programmed states may be attained by application ofrespective suitable differential voltages relative to conductivecapacitor electrodes 12 and 14, such as described in Strukov et al. “Themissing memristor found”, Nature Publishing Group, 1 May 2008, Vol. 453,pp. 80-83. For example, depending upon charge of the mobile dopants,suitable positive and/or negative voltages could be applied toconductive electrodes 12 and 14 to cause the mobile dopants to beattracted to or repelled from one of conductive electrodes 12 and 14,with the depicted example programming states of FIGS. 1 and 2 beingretained after the programming voltage differential is removed.

Memcapacitor device 10 of FIG. 1 may be schematically modeled as acapacitor C1 and resistor R1 connected in parallel. Although barrierdielectric material 18 effectively prevents current from flowing betweenelectrodes 12 and 14, barrier dielectric material 18 may conduct a verysmall and insignificant amount of leakage current. Resistor R1represents this leakage current. Capacitor C1 represents the capacitanceof memcapacitor device 10 in the FIG. 1 programmed state and representsthe combined capacitance of material 16 and barrier dielectric material18. Memcapacitor device 10 of FIG. 2 may also be schematically modeledas a capacitor C2 and resistor R2 connected in parallel. Resistor R2represents the insignificant leakage current of memcapacitor device 10in the FIG. 2 programmed state and which may be higher or lower than R1of FIG. 1. Capacitor C2 represents the capacitance of memcapacitordevice 10 in the FIG. 2 programmed state and which is larger than C1 ofFIG. 1. C2 represents the combined capacitance of material 16 andbarrier dielectric material 18.

Regardless, in one embodiment a memcapacitor device comprises a pair ofopposing conductive electrodes, for example conductive electrodes 12 and14. At least two materials are received between the opposing conductiveelectrodes. One of the materials comprises a crystalline semiconductivemetal-containing mass that is overall stoichiometrically cationdeficient to form mobile cation vacancies in a space lattice. In oneembodiment, the crystalline semiconductive metal-containing mass is acrystalline semiconductive metal oxide mass. The other material is abarrier dielectric material that is in physical touching contact withthe crystalline semiconductive metal-containing mass and that isimpervious to movement of mobile cation vacancies from said mass intothe barrier dielectric material. The semiconductive mass and the barrierdielectric material are of different composition relative one anotherwhich is at least characterized by at least one different atomicelement. One of the semiconductive mass and the barrier dielectricmaterial is closer to one of the pair of electrodes than is the other ofthe semiconductive mass and the barrier dielectric material. The otherof the semiconductive mass and the barrier dielectric material is closerto the other of the pair of electrodes than is the one of thesemiconductive mass and the barrier dielectric material. Examplematerials for the crystalline semiconductive metal-containing mass inthis embodiment include those described above for material 16. Examplematerials for a barrier dielectric material in this embodiment includethose described above for barrier dielectric material 18. Otherattributes in this embodiment may include any one or combination ofthose described above with respect to the example embodiments describedwith reference to FIGS. 1 and 2.

An embodiment of the invention encompasses a method of programming acapacitor between different static programmable states characterized bydifferent capacitance. Such may encompass using capacitors as describedabove, or using other capacitors. Regardless, an embodiment of suchmethod comprises applying a voltage differential between two conductivecapacitor electrodes to cause mobile dopants to move from asemiconductive mass received between the two conductive capacitorelectrodes toward a mobile dopant barrier dielectric material receivedbetween the two conductive capacitor electrodes to increase capacitanceof the capacitor from a lower capacitance state to a higher capacitancestate. The semiconductive mass and the mobile dopant barrier dielectricmaterial are of different composition relative one another which is atleast characterized by at least one different atomic element. The mobiledopant barrier dielectric material inherently shields mobile dopantsfrom moving into the mobile dopant barrier dielectric material byapplying of the voltage. Example mobile dopants, semiconductivemass/material and mobile dopant dielectric materials may be as describedabove. FIGS. 1 and 2 depict an example of such programming in going fromthe state of FIG. 1 to that of FIG. 2. Such may be accomplished byapplying suitable positive and/or negative voltages to capacitorelectrodes 12 and 14 which cause the mobile dopants to migrate towardelectrode 14 or away from electrode 12 thereby transforming theprogrammed FIG. 1 state to that of FIG. 2.

In one embodiment, a different voltage differential is subsequentlyapplied between the two conductive capacitor electrodes to cause themobile dopants to move away from the mobile dopant barrier dielectricmaterial to reduce capacitance of the capacitor and thereby program thecapacitor to one of said different static programmable states. Such may,for example, occur by programming the FIG. 2 state back to FIG. 1 bypolarity reversal from that which produced FIG. 2 from FIG. 1, or byapplication of some other suitable differential voltage to achieve thestated reduced capacitance effect. Further, such subsequently appliedvoltage differential may or may not program the capacitor back to theimmediately preceding capacitive state. Accordingly, programming to morethan two capacitive states may selectively occur.

An embodiment of the invention encompasses a field effect transistordevice which is capable of being repeatedly programmed to at least twodifferent static threshold voltage states. Such is shown by way ofexample only in FIGS. 3 and 4 with respect to a field effect transistordevice 30. FIG. 3 diagrammatically shows an example highest staticthreshold voltage state and FIG. 4 diagrammatically shows an examplelowest static threshold voltage state.

Transistor device 30 comprises a pair of source/drain regions 32, 34, achannel region 36 received between a pair of source/drain regions 32,34, and a gate construction 38 which is operably proximate channelregion 36. Source/drain regions 32, 34 and channel region 36 are shownas being formed within a suitable semiconductive material 38, forexample monocrystalline silicon. Material 38 would be suitablybackground doped at least in the region of channel 36 with at least afirst or second conductivity type dopant such that a current path may beselectively created between source/drain regions 32, 34 by voltageapplied to the gate. Source/drain regions 32, 34 are shown as beingconductive diffusion regions which have been suitably doped with atleast a conductivity enhancing dopant of opposite conductivity type tothat of channel region 36. Halo, L_(DD), or other regions, whetherexisting or yet-to-be developed, may be used with and/or as part ofregions 32, 36, 34. Transistor device 30 is diagrammatically shown asbeing a planar or horizontal transistor. Any other configuration iscontemplated whether existing or yet-to-be-developed, for examplevertical, recessed, and FinFet whether fabricated in bulk,semiconductor-on-insulator, or other substrates whether existing oryet-to-be-developed.

Gate construction 38 comprises a conductive gate electrode 40. Gateconstruction 38 also comprises both a semiconductive material 42comprising mobile dopants received within a dielectric and a mobiledopant barrier dielectric material 44, each of which is received betweenconductive gate electrode 40 and channel region 36. Mobile dopantbarrier dielectric material 44 is closer to channel region 36 than toconductive gate electrode 40. Semiconductive material 42 is closer toconductive gate electrode 40 than to channel region 36. Semiconductivematerial 42 and barrier dielectric material 44 are of differentcomposition relative one another that may or may not be at leastcharacterized by at least one different atomic element.

Example materials for conductive gate electrode 40 are the same as thatdescribed above for electrodes 12 and 14. Example semiconductivematerials 42, including properties and attributes, may be the same asthat described above for semiconductive material 16 of memcapacitordevice 10. Example mobile dopant barrier dielectric materials 44,including properties and attributes, are the same as those describedabove for mobile dopant barrier dielectric material 18 of memcapacitordevice 10.

Regarding respective thicknesses, semiconductive material 42 and mobiledopant barrier dielectric material 44 may be of the same or differentthickness. In one embodiment, mobile dopant barrier dielectric material44 is no thicker than material 42. In one embodiment and as shown,material 42 is thicker than mobile dopant barrier dielectric material44. In one example, material 42 has a thickness from 4 nanometers to 100nanometers, and in one embodiment has a thickness no greater than 20nanometers. In one embodiment, mobile dopant barrier dielectric material44 has an equivalent oxide thickness from 1 nanometer to 12 nanometers,and in one embodiment has such a thickness no greater than 7 nanometers.

As a specific example transistor device 30, conductive gate electrode 40consists essentially of elemental platinum having a thickness of 5nanometers. Mobile dopant barrier dielectric material 44 is ZrO₂ havinga thickness of 3 nanometers. Semiconductive material 42 is a combinationof TiO₂ and TiO_(2-x) and has as an overall thickness of 4 nanometers.In FIG. 3, region 48 has a thickness of 2 nanometers and is TiO₂ thathas sufficiently less than 5×10¹⁸ oxygen vacancies/cm³ which rendersregion 48 non-conductive. Region 46 has a thickness of 2 nanometers andan overall average oxygen vacancy density sufficiently greater than5×10¹⁸ vacancies/cm³ which renders region 46 conductive. In FIG. 4,region 42 may be considered as TiO_(2-x) having an overall averageoxygen vacancy density sufficiently greater than 5×10¹⁸ vacancies/cm³which is sufficient to render all of region 42 to be conductive. Overallaverage oxygen vacancy density in region 46 in FIG. 3 is greater thanthat in region 42 in FIG. 2.

The model respective threshold voltages in connection with the FIGS. 3and 4 model may be characterized as:

$V_{T} = {V_{F\; B} + {2\varphi_{B}} + \frac{\sqrt{q\; 2\; ɛ_{s}N_{a}2\varphi_{B}}}{C}}$C  is  gate  area  as  F/m²

where:

-   -   V_(T) is device threshold voltage    -   V_(FB) is flat band voltage    -   φ_(B) is potential difference of the channel fermi level and the        intrinsic Fermi level divided by the elementary charge    -   q is elementary charge    -   ∈_(s) is permittivity of Silicon    -   N_(a) is channel acceptor concentration    -   C is gate capacitance per unit area in F/m²    -   F is farads    -   m² is square meters

Field effect transistor device 30 may be programmed into at least one oftwo different static threshold voltage states as shown in FIGS. 3 and 4analogous to the programming with respect to the capacitance states ofcapacitor device 10 in FIGS. 1 and 2, respectively. For example in FIG.3, a region 46 of semiconductive material 42 is analogous to the FIG. 1region 20, and a region 48 of semiconductive material 42 is analogous tothe FIG. 1 region 22. Likewise, the programming state depicted for thefield effect transistor device 30 in FIG. 4 is analogous to theprogramming state of capacitor device 10 in FIG. 2, and which may beachieved for example as described below.

An embodiment of the invention encompasses a method of programming afield effect transistor device, for example device 30 or some otherfield effect transistor device. Regardless, such a method comprisesapplying a voltage differential between a channel region and a gateelectrode to cause mobile dopants within a material received between thegate electrode and the channel region to move toward one of the gateelectrode or the channel region to change a static threshold voltage ofthe field effect transistor device that is retained after said appliedvoltage differential is removed. In one embodiment, the applying of avoltage differential moves the mobile dopants toward the gate electrodeand increases the threshold voltage of the transistor device. Such isshown or may be considered, for example, in programming the field effecttransistor device of FIG. 4 to achieve the state of FIG. 3. In oneembodiment, the applying of a voltage differential moves the mobiledopants toward the channel region and decreases the threshold voltage ofthe field effect transistor. For example with respect to device 30, suchis exemplified by programming from the device state of FIG. 3 to that ofFIG. 4.

Programming of field effect transistor device 30 to either of the statesof FIGS. 3 and 4 may be performed in an analogous manner to thatachieved with respect to FIGS. 1 and 2 for capacitor device 10. Forexample in programming transistor device 30, conductive gate electrode40 may be used analogously to use of conductive electrode 12 incapacitor device 10 in FIGS. 1 and 2. Further, channel region 36 may beoperated such that it functions analogously to use of conductiveelectrode 14 in capacitor device 10 in FIGS. 1 and 2. For example,channel region 36 may be provided to a suitable voltage potential theresult of suitable selected current flow between source/drain regions32, 34, or by direct application of a voltage to source/drain region 36by suitable voltage application to material 38 outside of region 36.Further, multiple programmed threshold voltage states beyond two may beemployed.

Embodiments of the invention also encompass non-volatile memory arrays.Referring to FIG. 5, an example non-volatile memory array is indicatedgenerally with reference numeral 50. Such comprises a plurality of wordlines WL and a plurality of bit lines BL. Such are shown as beingstraight lines which orthogonally cross relative one another. Othershapes and angles of intersection, whether existing or yet-to-bedeveloped, may be used. Bit lines BL and word lines WL arediagrammatically and schematically shown in FIG. 5 as touching oneanother where such intersect, although such would not be ohmicallyconnected relative to the depicted intersections.

A plurality of memory cells, which are not specifically designated inFIG. 5, would be included in the non-volatile memory array of FIG. 50.Individual memory cells may be associated with each intersection of abit line BL and a word line WL. Alternately by way of example, a singlebit line may be associated with multiple memory cells with each havingits own associated word line, for example corresponding in design toNAND flash. Regardless, individual memory cells of the non-volatilememory array will comprise a field effect transistor device capable ofbeing reversibly programmed to at least two different static thresholdvoltage states. Such field effect transistor devices may comprisedevices as described above in connection with FIGS. 3 and 4.

Specifically in an example, FIGS. 6 and 7 depict incorporation of fieldeffect transistor device 30 in a non-volatile memory array such as thatof FIG. 5, and correspond to the programming states of FIGS. 3 and 4,respectively. In an individual memory cell composed of device 30,conductive gate electrode 40 would connect with one of word lines WLfrom FIG. 5. One of the pair of source/drain regions 32 or 34 wouldconnect with one of the bit lines BL, with source/drain region 34 inFIGS. 6 and 7 being shown as being so connected. A voltage potential maybe applied to the opposing source/drain region (i.e., region 32) that isnot connected with the one bit line for programming the individualmemory cell, for example into either of the at least two respectiveprogramming states depicted by FIGS. 6 and 7. Suitable CIRCUITRY wouldbe provided for reading the programmed state of each memory cell bysensing the programmed static threshold voltage state of the fieldeffect transistor device of each memory cell.

In one embodiment and as shown in FIGS. 6 and 7, CIRCUITRY may beprovided that is configured to enable a current to flow through the pairof source/drain regions 32, 34, the channel region 36, and the one ofthe bit lines BL to which source/drain region 34 connects when a voltageis applied to one of the word lines WL. In one embodiment, source/drainregion 34 may indirectly connect with the one example bit line via oneor more of the other memory cells. Such is diagrammatically shown inFIGS. 6 and 7 with respect to phantom depicted block 75 which isassociated with one or more memory cells in addition to the one memorycell depicted in FIGS. 6 and 7. For example, indirect connection to abit line may occur analogous to a single bit line being connected to astring of non-volatile charge-storage transistors in a NAND array ofmemory cells for example as shown in U.S. Pat. No. 7,476,588.

Regardless, in one example, a non-volatile memory array can beconstructed by using field effect transistor devices as described hereinwherein the gates are essentially programmable somewhat analogous to aflash transistor of a memory cell containing a flash transistor. Forexample, a floating body flash cell reversibly and statically retainsdata by shifting threshold voltage via charge-storage, wherein a memorycell incorporating a transistor as described herein is capable ofstoring reversible static data by varying the capacitance of the gatewherein the gate constitutes one electrode of a capacitor and thechannel region the other electrode of the capacitor. Traditional flashtransistors suffer from disturb issues as a result of stored charge inthe form of free electrons being capable of easy ejection from thefloating gates in which such are stored in one programmed state. Fieldeffect transistor devices and non-volatile memory arrays incorporatingsuch devices as described herein may be largely immune to any disturbissues as the mobile dopants would not be as readily ejectable, if atall, from the transistor as easily as free electrons are so ejectable inflash. Further, since stress-induced leakage current will accordinglynot be as significant a concern for data retention in a memory cell asherein described, the example dielectric material 44 may be fabricatedmuch thinner than the corresponding tunnel dielectric is fabricated inflash.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

The invention claimed is:
 1. A field effect transistor device capable ofbeing repeatedly programmed to at least two different static thresholdvoltage states, comprising: a pair of source/drain regions, a channelregion between the pair of source/drain regions, and a gate constructionoperably proximate the channel region; and the gate constructioncomprising a conductive gate electrode and comprising a semiconductivematerial comprising mobile dopants within a dielectric and comprising amobile dopant barrier dielectric material received between theconductive gate electrode and the channel region, the mobile dopantbarrier dielectric material being closer to the channel region than tothe conductive gate electrode, the semiconductive material thatcomprises mobile dopants within a dielectric being closer to theconductive gate electrode than to the channel region, the mobile dopantbarrier dielectric material comprising at least one of ZrO₂, SiO₂,Si₃N₄, GeN, and SrTiO₃.
 2. The device of claim 1 wherein the mobiledopant barrier dielectric material comprises ZrO₂.
 3. The device ofclaim 1 wherein the mobile dopant barrier dielectric material comprisesSiO₂.
 4. The device of claim 1 wherein the mobile dopant barrierdielectric material comprises Si₃N₄.
 5. The device of claim 1 whereinthe mobile dopant barrier dielectric material comprises GeN.
 6. Thedevice of claim 1 wherein the mobile dopant barrier dielectric materialcomprises SrTiO₃.
 7. A field effect transistor device capable of beingrepeatedly programmed to at least two different static threshold voltagestates, comprising: a pair of source/drain regions, a channel regionbetween the pair of source/drain regions, and a gate constructionoperably proximate the channel region; and the gate constructioncomprising a conductive gate electrode and comprising a semiconductivematerial comprising mobile dopants within a dielectric and comprising amobile dopant barrier dielectric material received between theconductive gate electrode and the channel region, the mobile dopantbarrier dielectric material being closer to the channel region than tothe conductive gate electrode, the semiconductive material thatcomprises mobile dopants within a dielectric being closer to theconductive gate electrode than to the channel region, the semiconductivematerial that comprises mobile dopants within a dielectric and themobile dopant barrier dielectric material being in physical touchingcontact with one another.
 8. The device of claim 7 wherein no othermaterial is received between the pair of opposing conductive electrodesbut for the semiconductive material that comprises mobile dopants withina dielectric and the mobile dopant barrier dielectric material.
 9. Afield effect transistor device capable of being repeatedly programmed toat least two different static threshold voltage states, comprising: apair of source/drain regions, a channel region between the pair ofsource/drain regions, and a gate construction operably proximate thechannel region; and the gate construction comprising a conductive gateelectrode and comprising: a crystalline semiconductive metal-containingmass received between the conductive gate electrode and the channelregion and that is overall stoichiometrically cation deficient to formmobile cation vacancies in a space lattice; and a barrier dielectricmaterial received between the conductive gate electrode and the channelregion and in physical touching contact with the crystallinesemiconductive metal-containing mass and that is impervious to movementof the mobile cation vacancies from said mass into the barrierdielectric material, the semiconductive mass and the barrier dielectricmaterial being of different composition relative one another which is atleast characterized by at least one different atomic element, thebarrier dielectric material being closer to the channel region than tothe conductive gate electrode, the semiconductive mass being closer tothe conductive gate electrode than to the channel region.
 10. A fieldeffect transistor device capable of being repeatedly programmed to atleast two different static threshold voltage states, comprising: a pairof source/drain regions, a channel region between the pair ofsource/drain regions, and a gate construction operably proximate thechannel region; and the gate construction comprising a conductive gateelectrode and comprising: a crystalline semiconductive metal oxide massreceived between the conductive gate electrode and the channel regionand that is overall stoichiometrically oxygen atom deficient to formmobile oxygen vacancies in a space lattice; and a barrier dielectricmaterial received between the conductive gate electrode and the channelregion and in physical touching contact with the crystallinesemiconductive metal oxide mass and that is impervious to movement ofthe mobile oxygen vacancies from said mass into the barrier dielectricmaterial, the semiconductive mass and the barrier dielectric materialbeing of different composition relative one another which is at leastcharacterized by at least one different atomic element, the barrierdielectric material being closer to the channel region than to theconductive gate electrode, the semiconductive mass being closer to theconductive gate electrode than to the channel region.
 11. The device ofclaim 10 wherein the barrier dielectric material comprises a metaloxide.
 12. The device of claim 11 wherein a metal of the metal oxide ofthe barrier dielectric material is different from a metal of the metaloxide mass.
 13. The device of claim 12 wherein the barrier dielectricmaterial comprises ZrO₂ and the crystalline semiconductive metal oxidemass comprises a combination of TiO₂ and TiO_(2-x).
 14. The device ofclaim 10 wherein the barrier dielectric material consists essentially ofstoichiometric metal oxide.
 15. The device of claim 14 wherein a metalof the stoichiometric metal oxide is different from a metal of the metaloxide mass.
 16. The device of claim 15 wherein the stoichiometric metaloxide comprises ZrO₂ and the crystalline semiconductive metal oxide masscomprises a combination of TiO₂ and TiO_(2-x) in at least one programmedstate.
 17. The method of claim 16 wherein the stoichiometric metal oxideconsists essentially of ZrO₂.